Guide pad mounting on a drill bit

ABSTRACT

A drill has a guide pad pivotally mounted on it, on that the guide pad may adapt itself to the surface of a hole wherein the drill is being operated.

United States Patent 11 1 Faber 14 1 Aug. 7, 1973 1 1 GUIDE PAD MOUNTING()N A 01111111 BIT 1,866,082 7/1932 011115011 175/202 9 {75] Inventor:Kurt Heinrich Albert Erich Faber, Sundvikcn, Sweden 2 47:726 1953Assigncc: Sandvik k g Sandvikcn BlShOp X Swede" FOREIGN PATENTS ORAPPLICATIONS [22] Filed: Nov. 20, 1970 313,802 6/1929 Great Britain175/325 271,839 3/1928 Great Britain.... 175/325 [211 APPl- 91,2961,221,024 5/1960 France 175 325 66,525 9/1914 Austria..... 175/325Foreign Application Priority Data 321,935 6/1920 Germany 175/325 N.24,1969 S 'd 16082 69 m w Ln Primary Examiner-Marv1n A. Champlon 52 us.c1 408/200 175/325 175/408 Lewis Attorney-Pierce, Scheffler & Parker[51] Int. Cl B23b.5l/00 [58] Field of Search 175/320, 325, 344-347, [57]ABSTRACT A dr111 has a gu1de pad p1vota11y mounted on it, on that [56]References Cited the guide pad may adapt itself to the surface of a holeUNITED STATES PATENTS 'wherein the drill is being operated. 2,151.6463/1939 Subkow ct a1. 175/325 7 Claims, 8 Drawing Figures PAIENIEmuc 1 mssum 1 or 4 7 PAIENIED AUG 71973 SHEET 3 BF 4 l I I I.

GUIDE PAD MOUNTING ON A DRILL BIT between the outer surface of the padand the wall of the hole. Now it has been observed that the shape of thedrill may change, for instance by elastic deformation or by diameterwear, in such a way that there is established only a partial contactbetween the pads and the wall of the hole. This results in an increasedspecific surface pressure from the pads causing undue friction.

The invention provides an improvement in this regard by means of a guidepad which is mounted on a pivot, so that it can rock and adapt itself tothe surface of the hole, thereby securing a full surface contact.

The invention is closer described in the following specification withappended drawings, showing:

FIG. 1, a side view of a drill according to the invention.

FIG. 2, an end view of the same drill.

FIG. 3, a guide pad on the same drill.

FIG. 4, a cross section on the line 4-4 in FIG. 3.

FIG. 5, a side view of another embodiment of the invention.

FIG. 6, an end view of the drill in FIG. 5.

FIG. 7, a side view of a third embodiment of the invention.

FIG. 8, an end view of the drill in FIG. 7.

The drill shown in FIGS. 1 and 2 is a metal drill having a number ofcutting inserts 11 clamped in supports 13 by clamps 12 of which allexcept one have been omitted in FIG. 2. The supports 13 are attached tothe drill in a suitable way, e.g., by screws or by brazmg.

For supporting and guiding the drill in the hole are provided two guidepads 20, suitably of sintered carbide. The pads are mounted on a pivotso that they can rock around both a longitudinal and a transverse axis.The pivoting around a longitudinal axisis obtained by means of a support21 witha cylindrical sliding surface 22, which rests on a matchingsurface 23 in a depression in the drill. The periphery surface 25 of thesupport 21 is approximately flush with the periphery surface of thedrill. The support is fastened with a screw 26 (FIG. 1) and a resilientwasher 27 permitting rocking of the support.

The pivot axis 24 lies outside the pad in order that when the drillrotates the friction on the pad will urge the leading edge 28 of the padaway from the edge of the hole. This lessens the friction andfacilitates the entering of the lubricant between the pad and the wall.By a suitable position of the centre 24 the surface pressure can beproperly distributed with regard to the hydrodynamic effect of thelubricant.

The pivoting on a transverse axis is obtained by a support 30 having acylindrical surface 31 sliding along a matching surface 32 in thesupport 21. The pad is held by a tubular pin 34 within a bore throughboth supports 21 and 30. As the axis of the pin lies outside the pivotcentre 33, the rocking requires bending of the pin. This is madepossible by an annular space 35 extending along a part of the pin 34.

The pivot mounting around two perpendicular axii provided by the abovedescribed two cylindrical sliding joints may be obtained by a singlespherical joint.

FIGS. 5 and 6 show a modified embodiment of the invention in which thepad unit 40 is symmetrical. It carries two sintered carbide pads 41 oneach side of a fastening screw 42, under the head of which there is ahelical spring 43 permitting the rocking around a longitudinal axis.This embodiment comprises no rocking on a transverse axis. The advantageof the symmetrical pad is that the pad can be turned half a turn when ithas been worn out on the side having the greatest pressure.

FIGS. 7 and 8 show another symmetrical pad unit 50 having four padinserts 51 on a drill for counterboring (reaming), i.e. for enlargingthe internal diameter of holes. The specific advantage is that the greatarea of the pads makes the'tool suitable for reaming the inner diameterof tubes with a thin wall that would be damaged by the pressure fromsmaller guide pads.

'I claim:

1. Drill for drilling in metal having a guide pad adapted to slide withfrictional contact along the wall of the drill hole, in which the guidepad is pivotally rockable on at least one axis having the same generaldirection as the sliding surface of the guide pad and situated at afixed distance from the drill axis.

2. Drill as defined in claim 1, in which the guide pad is mounted on asliding bearing with a curved sliding bearing surface.

3. Drill as defined in claim I in which the pivot comprises acylindrical sliding bearing with a longitudinal axis.

4. Drill as defined in claim 3, in which the pivot comprises a secondcylindrical sliding bearing with a transverse axis.

5. Drill as defined in claim 1 in which the pivot comprises a sphericalsliding bearing.

6. Drill as defined in claim 1 having a guide pad on a longitudinalpivot axis, in which said axis lies outside the periphery surface of thepad.

7. Drill as defined in claim 1, in which the pivoted guide pad isrockable about longitudinal and transverse axes whereby said guide padadapts itself to the surface of a hole in which said drill isbeingoperated.

I I l l

1. Drill for drilling in metal having a guide pad adapted to slide withfrictional contact along the wall of the drill hole, in which the guidepad is pivotally rockable on at least one axis having the same generaldirection as the sliding surface of the guide pad and situated at afixed distance from the drill axis.
 2. Drill as defined in claim 1, inwhich the guide pad is mounted on a sliding bearing with a curvedsliding bearing surface.
 3. Drill as defined in claim 1 in which thepivot comprises a cylindrical sliding bearing with a longitudinal axis.4. Drill as defined in claim 3, in which the pivot comprises a secondcylindrical sliding bearing with a transverse axis.
 5. Drill as definedin claim 1 in which the pivot comprises a spherical sliding bearing. 6.Drill as defined in claim 1 having a guide pad on a longitudinal pivotaxis, in which said axis lies outside the periphery surface of the pad.7. Drill as defined in claim 1, in which the pivoted guide pad isrockable about longitudinal and transverse axes whereby said guide padadapts itself to the surface of a hole in which said drill is beingoperated.